I came across this note that I'd left myself, a story idea which I never started on: "Free matter, but cannot ever be moved or transformed. It's plastic." The idea of that was to explore what would happen if we could literally build anything we wanted, with no material or construction costs, but these creations would be permanent. Would we fill up the world with junk or build almost nothing out of fear of the junk? Who would have the ability to build?

The part that amuses me is the note itself and how it is phrased. I used the term plastic in reference to the common perception of plastics as substances which do not decay and unless we directly act to destroy them, tend to stay around for a very long time. But plastic is also an adjective, meaning something which can be molded or take a shape, in effect, things which can be changed, the exact opposite of my permanent buildings.